The following specification relates to fiberglass molding processes. More particularly, the invention relates to vacuum assisted resin impregnation of fiber reinforced lay-ups in molds.
The most similar prior art is shown in U.S. Pat. No. 4,942,013 which teaches permeable cores used in fiberglass construction between sheets of fiberglass matting (see FIG. 10 of the ""013 patent discussed below). The prior art shows the use of vacuum technology for vacuum impregnation of a fiber reinforcement such as carbon cloth with a resin to produce a resin-fiber composite. Some patents covering this technology and narrowing the specific search somewhat are:
U.S. Pat. No. 4,902,215 issued on Feb. 20th, 1990 to Seemann, III.
U.S. Pat. No. 5,052,906 issued on Jul. 17th, 1990 to Palmer et al.
U.S. Pat. No. 5,316,462 issued on May 31st, 1994 to Seemann.
U.S. Pat. No. 4,942,013 issued on Jul. 17th, 1990 to Palmer et al.
The ""013 patent is probably the closest art of this group.
The most important advance taught by the present specification improvement lies in running a channel through the fiber reinforcement cloth to the permeable core. Compare the language in the ""013 patent:
xe2x80x9cFIG. 10 is a prospective [sic] view of a foam core having slots in the surface thereof to function as resin flow paths for resin impregnation of fiber reinforcement skins to be positioned on the foam core . . . xe2x80x9d P.6 lines 20-25.
xe2x80x9cThe provision of the resin flow channel formed by grooves 160 and 162 in the foam core 158 achieves large area, rapid impregnation of the cloth skins on both surfaces of the sandwich . . . xe2x80x9d P.12 lines 35-45.
xe2x80x9cA porous separator film 173 is located over the complete lay-upxe2x80x9d
In this way the core, which is sandwiched in the middle of the cloth layers, serves as a conduit for the resin to move throughout the mold. xe2x80x9cHow, in FIG. 10A does the resin get to the core to spread out throughout the mold?xe2x80x9d
claim 19 of the ""013 patent addresses this as follows:
xe2x80x9cDrawing of a vacuum to permit passage of the liquid resin through said resin inlet line,
Flowing said resin through a path defined by said bleeder layer,
Flowing said resin from said bleeder layer through and along said fiber reinforcement layer, and
Flowing said liquid resin from said fiber reinforcement layer into said grooves (in the core) of said supporting block and from said grooves back into said fiber reinforcement layer.xe2x80x9d
The question is answered in our embodiment, by cutting a channel through the cloth to reach a flexible or non-flexible woven core.
The question of providing adequate impregnation of a mold without expensive materials or waste is answered in this proposed specification. The most immediate improvement is defined by cutting a channel through the cloth to reach a woven core.
One limitation which is not included in the prior art discussed above for this improvement can be shown by the following claim language:
As can best be seen by reference to FIG. 1 of the invention, a non-absorbent porous layer 2 is positioned between a top fiberglass resin absorbent layer 5 and a bottom fiberglass resin absorbent layer 4. This lay up 36 comprised of layers 2, 4 and 5 communicates with a resin source (not shown, but this may be nothing more than a bucket containing resin) by way of tube 1. The tube 1 enters the top of the mold top 18. An entry means comprising an opening or channel 15 defined in the top absorbent layer 5 is located directly below where this opening 7 opens into the interior of the mold and this channel 15 is sufficiently large to allow the resin to reach the non-absorbing layer 2 at a desired rate. This channel 15 also allows the resin to reach the porous non-absorbing layer 2 without a sufficient amount of dissolved absorbing material to clog up the pores in the porous non-absorbing layer 2.
In the preferred embodiment, the non-absorbent layer 2 is a weave of non-absorbent fibers so that the spaces between the weaves provides the channels. However, the use of other inflexible materials (plastics, glass, wood, etc) with channels defined through the inflexible material as well as along the plane defined by the wood could be used for similar purposes. Examples of solid cores, as opposed to woven cores, includes wood having grooves, channels or holes throughout the surface and foam having grooves, channels or holes throughout the surface; metal woven from fibers or having grooves, channels or holes throughout the surface. Examples of woven cores include plastic woven fibers or woven or knitted non-absorbent monofilament, greenhouse shading, etc. The channels 3 within the weaves work best when they are usually between 0.0075 inches and 0.60 inches.
In most applications, the top opening or passage 15 would be at least 25% of the diameter of the input opening 7 through which the resin enters the combination so described. Generally, the size of this passage may still continue to function with some success having a width of {fraction (1/16)}th inch to 3 inches and a depth of {fraction (1/16)}th to 3 inches with very small molds. The size and depth of the hole will vary with the diameter of the mold and the amount of pressure used to draw the resin into the mold.
The invention is further defined as comprising a resin source for supplying resin to at least three layers so defined. This resin source is typically defined in terms of a tube 1 supplying resin into a relatively air-tight mold. The resin is drawn into the mold when a vacuum is applied to the mold. Because of the unique features of this technique and lay-up, it may also be defined in terms of injecting resin under a pressure into a mold without a vacuum since the current invention may be practiced with the resin under pressure because of the benefits associated with the internal distribution medium with unrestricted access to the resin source. A drain would still be necessary to bleed air out of the mold as the resin fills the mold, but many advantages would be apparent such as a more carefull control over the amount of resin injected into the system; having the lay-up cure under pressure; and, with large molds, such as ship hulls, pressure may be necessary since it may be impractical to put the entire mold under a vacuum.
The mold 6 has a top 18 which defines an input opening 7 substantially or approximately over the passage 15 in the absorbing layer. This passage 15 may be an opening in the reinforcing top layer 5 or it may be filled with non-absorbing mesh. In addition to the general parameters set forth above for the passage 15 defined by the top layer of absorbing material 5 (that it be at least {fraction (1/16)}th inch or 25% of the size of the opening through which the fiberglass resin enters the mold). The passage 15 can also be more narrowly defined as being at least xc2xd the size of the opening 7 or ⅓ of an inch in diameter to get the full benefit of the opening. For normal conditions, that is molds using standard resin of normal size, temperature and pressure. these limitations are more suitable.
Similarly, there may be more than one passage 15 within the scope of the invention set forth herein where larger molds are utilized allowing for the size of the passages 15a-15b to be smaller as shown in FIG. 7. Though only two passages 15 are shown in FIG. 7, it is obvious that the number may vary considerably. For example, if a boat hull was constructed using this technique, there could be several hundred passages 15, all receiving resin under pressure or all subjected to a common vacuum.
Substantially smaller passages 15 in the absorbing top layer 5might result in a portion of the absorbing material fouling the passage 15 and affecting resin flow throughout the non-absorbent layer 2. Also material from the top layer might flow into the non-absorbent layer 2 clogging the channels 3 in the non-absorbent layer 2. The function of the passage 15, is therefore seen to be (1) preventing the inflow of absorbing material into the non-absorbent layer 2 and (2) to prevent the expanding absorbing material from clogging the flow of resin through the passage 15.
The non-absorbent porous layer need only be substantially non-absorbing, since under some circumstances, the absorption of fiberglass could have a desirable effect as long as the overall function of the channels 3 was not affected. It is also clear from this discussion that having a weave of non-absorbing material having a series of passages, at least one of which was {fraction (1/16)}th inch would also function. The main limitation in the size of the passage 15 is that when the hole exceeds a certain size, the beneficial effect of the reinforcing top layer 5 is missing at the inlet site. By having multiple inlet openings 7 and multiple passages 15, this problem may be avoided.
The non-absorbing layer 2 may be defined as being substantially non-absorbing. Substantially non-absorbing simply means that it does not degrade or swell with the absorption of the fiberglass resin sufficiently to substantially impair the flow of resin through the channels defined by the non-absorbing layer 2. Substantially impair flow means that the flow would be so impaired so as to improperly fill the lay-up 36 to the requisite extent.
Other additional limitations which are important to more narrow versions of the invention includes the limitations on the diameter of the opening defined and sandwiching the core between layers of reinforcing fiber so that the core becomes a part of the mold. Various modifications of the core to make this construction stronger are also taught.